Some human pathogens are natural members of the marine microbial community (e.g Vibrio species), but many others, such as the protist Giardia, are potentially introduced into seawater from sewage input and terrestrial runoff. Despite the potential for their impact on human health, relatively little is known about the occurrence, much less the prevalence and distribution, of traditionally non-marine human pathogens. The survival and persistence of various pathogens is most certainly influenced by environmental conditions, and the contamination of coastal and estuarine areas through freshwater runoff, sewage and thermal pollution have the potential to alter local environmental conditions. Studies that examine pathogen presence and persistence need to be coupled with predictive models in order to begin to determine where and when the risks of potential infection, or simply the presence of pathogens, are highest. Our project aims are to use molecular methodology to determine the distribution and abundances of the human pathogens (including Giardia, Cryptosporidium, Acanthamoeba, Naegleria, Vibrio and LegioneIla), determine whether naturally occurring marine amoebae can serve as reservoirs for pathogenic bacteria, and look for evidence of natural occurrence of these associations in the anthropogenically impacted estuarine environment of Mount Hope Bay, MA. Data will be collected over spatially and temporally relevant scales (multiple sites, multiple years). Information on the physico-chemical characteristics will be correlated with biological distribution and persistence information for use in evaluating a water quality/eutrophication model for the bay that could be used to predict where and when pathogens could be found.